Path loss is a measure of signal attenuation. Path loss is the difference between the transmitted signal power and the received signal power. Path loss has the units of Decibels (dB) and is a positive quantity which excludes the affects of the antenna gains. In its simplest form, path loss can be defined according to the free-space model of equation (1):PL(dB)=Pt−Pr  (1)where PL denoted path loss, Pt is the signal's transmitted power level and Pr is the signal level recorded at the receiver, measured in units of decibels, such as dBm. Equation (1) assumes that there is no antenna gain at the transmitter and the receiver.
Path loss is least pronounced where a visible line of sight is available between the transmitter and the receiver where there is little or no electromagnetic interference. Electromagnetic interference is typically in the form of co-channel interference. Conversely, path loss is more pronounced as obstacles and electromagnetic sources interfere with signal propagation. Because path loss is a measure of signal attenuation, and therefore, bit error rate, it is an important tool in measuring quality of service throughout a wireless network.
In wireless networks, service quality across geographic areas is audited by conducting drive tests. In such tests, a transmitter is positioned at different locations to send a beacon signal. The transmitter's signal level and the location of the transmitter are recorded. The receivers then record the received signal level. Using the transmitted and received signal levels, path loss between the two locations can be computed.
The conventional testing method has several deficiencies. For example, the drive test is time consuming and inefficient. The drive test is usually also limited to locations that are easily accessible to drive test operators. Therefore, it is likely that not all network locations would be subject to the path loss study. Another problem is that the beacon signal maybe degraded by noise and interference such that the receiver cannot accurately measure the signals, therefore are limited in their ability to compute true path loss. Accurate assessments of path loss are important for determining the wireless coverage areas in a network, and provide the basis for performing wireless network optimization. Network optimization is a critical process used by network operators to maintain an acceptable balance between infrastructure costs, service quality, and network capacity. In theory, this balance is best achieved through continuous monitoring of the network performance in all areas of the wireless network, which is traditionally not a cost-effective option for network operators. The disclosed invention addresses this issue and offers a method in which wireless network operators can maximize the effectiveness of network optimization through accurate and efficient assessments of path loss. The efficiency aspect is achieved by utilizing the wireless users as autonomous test points, whose locations are computed by a location system. High accuracy measurements of path loss may be computed simultaneously by the location system and made available as a continuous source of data needed for network optimization.